Electrolytic capacitors have characteristics of being compact and having large capacity, and are broadly employed as a configuration part of various electronic instruments, in-car equipments, and the like. An electrolytic capacitor comprises an anode foil having an oxide film on the surface, a cathode foil, and a separator, and has a structure consisting of an element obtained by interpositioning and winding a separator between the anode foil and the cathode foil and soaking this in an electrolytic solution. A solution of boric acid or carboxylic acid, or an ammonium salt thereof etc. dissolved in a flammable organic solvent such as ethylene glycol and γ-butyrolactone is used here as the electrolytic solution.
For this reason, when excessive electrical stress is applied to the electrolytic capacitor and the safe valve is set off, there is a risk that sparks generated from short circuiting etc. will ignite the gasified electrolytic solution and burn the element. Accordingly, there have been investigations to render flame-retardancy to electrolytic capacitors.
Patent Literatures 1 and 2 disclose a method of employing a flame-retardant separator. With this method, although the burning of the electrolytic capacitor itself is suppressed, rendering flame-retardancy to the electrolytic solution component that is ejected from the safe valve is difficult. On the other hand, Patent Literatures 3 and 4 disclose a technology of adding a phosphate ester such as trimethyl or triethyl phosphate to the electrolytic solution to render flame-retardancy in order to prevent the electrolytic solution component from burning.